AGO BAY Toward a New Sato-Umi

Mie Prefecture Fisheries Research Institute,

Please feel free to contact Mie Prefecture Shima City Fisheries Research Institute. TEL ᾉ +81-599-53-0130 Contents

More than 50 yyg,gyears ago, Ago Bay was a Sato-Umi*. 1ώGeographical Features , Land Use and History 1 Many kinds of organisms lived in the bay. 2ώFisheries 5 People enjoyed its many blessings, 3ώLiving Beings 9 such as catching clams, fishing and swimming, etc.

Understan 4ώTidal Flats and Sea Grass Beds 13 5 Pearl Culture 21 After World War ϩ, ώ social systems changed drastically, 6ώSediment and Water 25 d and Ago Bay lost its identity as a Sato-Umi. 7ώAutomatic Environmental Monitoring System 27 8ώWater Quality 29 “Have you visited Ago Bay recently ?” 9ώSeawater Flow and Seawater Exchange 35 10 Present Status of Ago Bay 43 ḛDo you know its many wonders ?” ώ We wrote this booklet for everyone

to be able to have more fun in Ago Bay. T hink 11ώRdTidRed Tides 45

We are making Ago Bay into a “New Sato-Umi”, 12ώHypoxia in Ago Bay 47 And we hope you find this booklet useful!

13ώAccumulation of Organic Materials and 51

Act Purification Capacity όḛSato-Umi” refers to an original Japanese concept that attaches great 14 Towards Nature Restoration in Ago Bay 55 importance to the relationship between local communities and the sea. ώ A Sato-Umi is the coastal area between the actual land and fisheries, with 15ώMore Information 61 high productivity and biodiversity in terms of human activities. 1ώGeographical Features, Land Use and History 1ώGeographical Features, Land Use and History Shape of Ago Bay ẔComplex Coastlinesẕ Mie Prefecture Ago Bay has an intricate coastline, known as a ria-type coast. ẔNo Long Rivers ẕ Principal rivers are the HIYAMAJI, HAZAKO, NISHIKAWA and MAEGAWA.

Areaᾉ26 km 2 Coastᾉ140 km Depth Ago Bay is located in the Maxᾉ40m ISE-SHIMA national park Bay mouthᾉ12m Width of bay mouthᾉ1.7 km ẔShima cityẕ

In Oct. 2008, Shima City was formed with the merger of 5 towns HUKAYA channel (Ago-cho, Isobe-cho, Shima-cho, Daio-cho and Hamajima-cho) ẔShallow Watersẕ The inner part of the bay is about 5m, with a maximum of about 40m SHIOYA UGATA and a bay mouth depth of 12m. Because the bay mouth is shaped like a HAZAKO SHINMEI bottle neck, water exchange is not simple. KASHIKOJIMA HAMAJIMA OSAKI TATEGAMI

Sha llow MASAKI NAKIRI

GOZA HUNAKOSHI Cross section KOSHIKA HUKAYA Depth of bay mouthᾉ12m Deepest WAGU KATADA Outer bay Ago Bay HUSEDA ขẟ ෌ẟ Bay mouth Areas around Ago Bay Inner part of bay 1ώGeographical Features, Land Use and History 1ώGeographical Features, Land Use and History Land Use Around Ago Bay History of Ago Bay and Pearl Culture Ago Bay is very famous for pearl culture. Because of its Forest Farmland harmony between nature and pearl culture, Ago Bay was Rice field designated as the first National Park after World War ϩ. Residential Factory Shop Road ẔHistory of Ago Bayẕ Uncultivated The Edo era [Beginning of land reclamation] Golf River 1668῍1704 Rice fields were constructed by land reclamation.

The Meiji era [Beginning of pearl culture] 1893 Kokichi Mikimoto produced a semi-circular pearl .

The Taisho era [Spread of pearl culture] 1923 Mie Prefectural Fisheries Research Institute started seed collections of ppyearl oysters.

The Early Showa era [Reduction of pearl culture] 1932 The Fukaya channel was constructed in Ago Bay. 1942῍1945 Reduction of pearl culture due to WWϩ.

The Middle Showa era [Development of pearl culture and setbacks] 1946 Ago Bay was designated the first Japanese National Park. ẔSurrounding Forestsẕ 1950῍ Rapid development of pearl culture. More than 50% of the land is forest. 19.4% of the land is made up 1959 Heavy damage from typhoon “Isewan”. of building lots, factories and roads. 1960 Heavy damage from a tsunami from Chile.

Because there is little flat land available around Ago Bay, rice The latter Showa era [Decline of pearl culture fields and farms are not very large. The surrounding forests allow and development of tourism] 1966 Drop in pearl culture from low quality and overproduction. rain to flow right into the bay. ῍ 1976 Pearl oyster seed production was developed. 1988῍ Development of leisure facilities was promoted. 2ώFisheries 2 Fisheries Aquaculture in Ago Bay ώ

Laver net Drain off water Press

Remove impurities Harvesting machine Harvesting

Drying Green laver Miso soup

ẔPearl Cultureẕ ẔCultivation of Green Laverẕ Ago Bay is very famous for being the cradle of pearl culture. In Ago Bay, green laver culture is booming. From autumn to In 1893, Koki c hi Mikimoto succee de d in pro duc ing a sem i-cilircular spriling, laver ne ts are p ldlthtdlaced along the coast,and are a tiltypical pearl for the first time in the world. After this success pearl culture sight all over the Bay. Harvested green laver is sold after drying. prospered in Ago Bay. Mie prefecture holds about a 60% share of the green laver in Japan, with Ago Bay contributing about 50% of Mie’s product. 㻝㻢㻜 ඲ᅜThroughout Japan Fishermen work hard to Mie prefecture ୕㔜┴ Green laver absorbs CO2 produce high quality pearls. 㻝㻞㻜 㻡㻜㻜 and nutrients in sea water, Mie prefecture୕㔜┴ Pearl production in Mie 㻤㻜 㻠㻜㻜 and also produces oxygen by 㻟㻜㻜 ⏕⏘㔞䠄㼠䠅

ppygrefecture always ranks high 㻠㻜 ᣽ųᲢᳮᲣ phthotosyn thithesis, thus prov iging 㻞㻜㻜

in Japan. ဃင 㻜 to be very useful to the 㻝㻜㻜 㻝㻥㻠㻡 㻝㻥㻡㻡 㻝㻥㻢㻡 㻝㻥㻣㻡 㻝㻥㻤㻡 㻝㻥㻥㻡 㻞㻜㻜㻡ᖺ 㻜 Changes in pearl production. environment. 㻝㻥㻠㻡 㻝㻥㻡㻡 㻝㻥㻢㻡 㻝㻥㻣㻡 㻝㻥㻤㻡 㻝㻥㻥㻡 㻞㻜㻜㻡 ᖺ Changes in green laver production. 2ώFisheries 2ώFisheries Coastal Fisheries in Ago Bay

There are various kinds of coastal fisheries in Ago Bay. ẔClamẕ Clams were gathered everywhere in Ago Bay until 1990. However, now there are very few. It is thought ẔSea Cucumberẕ that environmental changes and harmful red tides are Clam Sea cucumbers inhabit the sea bottom. Fishermen catch the main reasons why clams have disappeared. them with a net and hook from their boats. Fisheries of Sea cucumber sea cucumber are very famous around the HAMAJIMA ẔOther Fisheriesẕ region, and are called “HISHI-TSUKI-RYO”. Japanese black porgies and sting rays can be caught by grill nets. Around the bay mouth, Sargassum ẔPrawnẕ fusiforme and Gelidiaceae can be found. Prawns crawl about the sandy sea bottom. Fishermen Ge lidiaceae catch them with grill nets. The seeds of prawns are Prawn produced at the Fish Farm Center, and then these seeds are released into the sea.

ẔNemacystis Decipiens and Codium Japanese black porgy Sting ray Sargassum fusiforme Mucronatumẕ Changes of Catchment in Ago Bay Nemacystis decipiens can be gathered in March and Nemacystis decipiens Ẕ ẕ April. Codium mucronatum is collected in summer with a Until 1960 , more than 600t of aquatic products (shellfish, sea cucumbers, net. Nemacystis decipiens can be eaten with vinegar, and prawns and seaweed) were caught in Ago Bay. However, since 1965, this Codium mucronatum is eaten dipped in miso and vinegar amount has decreased dramatically. sauce after boiling.

 ẔSwimming Crabẕ Codium mucronatum Changes in aquatic products ƦƷ˂Other in Ago Bay ȊȞdzSea cucumber Swimming crabs can be gathered by grill nets or cages  ǯȫȞǨȓȷǬǶȟPrawn and crab in early summer. Their claws are so strong they can cut ෙᕹSeaweed through a twig. Swimming crabs can be eaten after  ᝝᫏Shellfish ᣽ųᲢᳮᲣ nt boiling. ྒྒ

๤  Amou Swimming crab  Pictureᾉ Faculty of bioresources, Mie University, Department of Fisheries, Mie Prefecture           3ώLiving Things 3ώLiving Beings Living Beings in Ago Bay Hibiscus hamabo communities are seen along the coast in Ago Bay. More than 50 years ago, there were a continuous Inner part of the bay natural coastal ecotones (reeds Ѝtidal flats Ѝseagrass beds) . There should be a lot of biodiversity in these areas. However, nature around Ago Bay has being lost because of development, Bay mouth leaving just a few kinds of living things in the coastal area. In order to restore the bay to a “Sato-umi”, we have to

N understand the environmental situation. If living beings increase, we will be able to enjoy the many blessings of Ago W E 2km Bay (catching shellfish, fishing, etc.). S

Callianassa japonica Hibiscus hamabo Bursatella leachii Clam

Zostera marina Sea slug Zostera japonica Reed Inner part

Zostera of the bay Reticunassa festi῅a Ilyoplax pusilla

Zostera marina Zostera japonica Tidal flat

Clypeaster japonicus Sea anemone Hypodytes rubripinnis

Apogon niger Halophila ovalis Balloon fish Feather-stars Echinocardium cordatum

Seaweed pipefish Bay mouth Zostera bed Nameᾉ Hypodytes rubripinnis Halophila ovalis Zostera japonica A diver 3ώLiving Beings Photo locationᾉ Hamajima Tategami Tategami Tategami Depthᾉ12m 5m 1m 2m

About 10cm long . Hypodytes Halophila ovalis grows in shallow Zostera japonica grows in inter tidal To investigate a Zostera bed , divers rubripinnis has strong poison on the areas. The leaves are oval and 1-3cm areas from Hokkaido to Okinawa. The must wear an oxygen tank in Ago Bay. dorsal fin. This fish is nocturnal, and long. leaves are about 3mm wide, and 20cm lives in Zostera beds. long.

Clypeaster japonicus Zostera marina Reticunassa festi῅a Callianassa japonica Hamajima Tategami Tategami Tategami 12m 2m 1m 2m

About 10cm long. Clypeaster Zostera marina grows in shallow About 3cm long. Reticunassa festi῅a About 5cm long. Callianassa japonica japonicus has a petal -like pattern on areas. The leaves are 0. 5-151.5m lon g lives on the surface of tidal flats. It digs a nest about 1m deep into the its body. Although it doesn’t have and taste sweet. More than 50 years eats dead fish and shellfish. tidal flats. needles, it belongs to the sea urchin ago, Zostera marina was used as family. fertilizer for farming.

SdifihSeaweed pipefish AiApogon niger Bursa te lla leac hii Shor tnec kc lam Hamajima Hamajima Tategami Tategami 12m 10m 1m 0m

About 20cm long. Seaweed pipefish About 10cm long. Apogon niger has About 5-10cm long. Bursatella leachii About 3-5cm long. Shortneck clams live in calm zostera beds. They coil big eyes. It comes to the Zostera has a green -brown body with many live in tida l fla ts. They can beea ten around Zostera marina. beds for spawning. spines. in miso soup and spaghetti. Nowadays they cannot be gathered in Ago Bay.

Sebastes inermis Echinocardium cordatum Atylus swammerdami Ilyoplax pusilla Hamajima Hamajima Tategami Tategami 12m 10m 1m 0m

About 20cm long. Sebastes inermis About 10-15cm long. Echinocardium About 2-5mm long. Atylus About 1cm long. Ilyoplax pusilla lives has big eyes. They live in Zostera cordatum belongs to the sea urchin swammerdami lives in the Zostera in tidal flats. It dances while moving beds. Sometimes they swim hovering family. It moves quickly by using its beds. It eats detritus, and plays an its claws. around the Zostera beds. spines. It lives on the sandy bottom. important role as food for many animals.

Bay mouth Inner part of the bay 4ώTidal Flats and Sea Grass Beds 4ώTidal Flats and Sea Grass Beds Tidal Flats Function of Tidal Flats

Estuary tidal flat at ANO river, MIE pref.

Tidal flats are coastal wetlands where mud is deposited by tides ẔFunction of Habitatsẕ or rivers. They are submerged and exposed approximately twice There are many living beings in tidal flats such as crabs, daily. Tidal flats are typically important regions for wildlife, shellfish and polychaeta. Many juvenile fish live there, too, supporting a large population, although the level of biodiversity and migratory birds use tidal flats as feeding and resting is not particularly high. They are often of particular importance grounds. to migratory birds . Thus they are called “nursery grounds”. Tidal ẔFunction of Natural Purification ẕ flats are good fishing grounds for shellfish. In tidal flats, bacteria decompose organisms from the land Because tidal flats are on the boundary between land and sea, and clams eat plankton by filtering sea water. Birds and fish they are very important areas for recreation and shellfish feed the macrobenthos and control the populations. That’s gathering. how sea water becomes clean. Thus all living beings contribute towards natural purification. 4ώTidal Flats and Sea Grass Beds 4ώTidal Flats and Sea Grass Beds Tidal Flats in Ago Bay Historical Changes in Tidal Flats

Tida l flats i n A go B ay are cl assifi ed as f oll ows.

ẔExistant tidal flatẕ

Ṳ Estuary tidal flats ίsand-mudὸ Formed at the mouth of a river. They have high biodiversity because of a sufficient supply of nutrients from land. ex. Ugatahama, Hazako, Hiyamaji 2004.7.25 Ṳ Foreshore tidal flats ίsandὸ ẔExistant Tidal Flatẕ 1% Formed in a small bay without rivers. 30% Estuary tidal flats 3ha They have low biodiversity because of Foreshore tidal flats 81ha insufficient nutrient supply. ẔReclaimed Areaẕ ex. Inner part of the bay 69% Reclaimed areas 185ha ẔReclaimed areaẕ Ṳ Reclaimed areas ίmudὸ More than 50 years ago, there were about 269ha of tidal flats in Ago More than 50 years ago, these areas Bay. That’s about 10% of the sea surface area. However the tidal flats were natural tidal flats. Now they have were reduced to construct rice fields. And even worse, the natural become unused wetlands. purification ability and biodiversity also decreased. Now, more than They ha ve low biodiversit y beca u se of 80% of reclaimed areas have become unused wetlands . If these areas environmental deterioration. are restored to tidal flats again, the natural purification ability and ex. Inner part of the bay (behind dykes) biodiversity may increase in Ago Bay. 4ώTidal Flats and Sea Grass Beds 4ώTidal Flats and Sea Grass Beds Zostera Beds Life Cycles of Zostera marina

Zostera marina

Growing period Growing period ίWinter῍Springὸ ίAutumn῍Springὸ Inflorescence

Reprodu- ctive Vegetative reproducing UGATA ᾉZostera beds shoots shoots by roots

SHINMEI Seedling TATEGAMI Withering period HAMAJIMA (Autumn Producing seeds ίSummerὸ -Spring) ίSpring῍Summerὸ Seeds (Summer) HUKAYA HUSEDA KATADA Zostera marina have two reproduction types, sexual and vegetative. Almost all Zostera marina are vegetative. ZtZostera mar ina are more wide ly known as “seagrass ”. They The vegetative type grows by spreading its roots from autumn produce seeds by flowering, which is different from seaweed. to spring and enlarging its leaves. In summer, its leaves wither They live on sand and mud coasts everywhere in Japan. They and shorten. After that it grows again by producing leaves from grow about 1.5m high from autumn to spring. In summer, their the remaining roots. roots wither and they float to the surface. Some vegetative types change to sexual types. In spring, they The areas where the zostera grow are called “zostera beds”. produce seeds by inflorescence. In summer, their leaves and In Hamajima and Hukaya, they grow in sand, but in Ugata, roots wither. The seeds droppp to the sea bottom and sprout due Shinmei, Tategami and Huseda, they grow in mud. to the low water temperature in autumn. 4ώTidal Flats and Sea Grass Beds 4ώTidal Flats and Sea Grass Beds Function of Tidal Flats Zostera Beds in Ago Bay

UGATA Sunlight

SHINMEI

Oxygen TATEGAMI HAMAJIMA Sexual type ᾋZostera bedᾍ Fish CO2 Nursery ground for ᾉZostera beds aquatic organisms

HUKAYA Macrobenthos HUSEDA KATADA Nitrogen and phosphorus Vegetativ e ty pe

In Zostera beds, the waves and water currents are reduced by The Zostera marina in Hamajima and Hukaya are vegetative zostera marina. Because there are many hiding places , Zostera types. Other areas have the sexual type. These are rare and beds are perfect as nursery grounds for aquatic organisms (fish, only grow in certain areas of Japan. shellfish, shrimp and crabs). Therefore, they are called the “cradle of the sea”.

Zostera marina absorb CO2 and nutrients in seawater and ẔZostera japonicaẕ produce oxygen by using sunlight. Therefore Zostera beds are Zostera japonica belong to the Zostera marina ideal for aquatic organisms. The amount and diversity of family but grow in shallower water. They are aquatic organisms in Zostera beds are more than 10 times smaller and more difficult to displace because of their strong roots. They grow in Ago Bay. larger than those areas without. Zostera beds are very Zostera japonica important places to protect biodiversity. 5ώPearl Culture Pearl Culture in Ago Bay Cultivation Cycle in Ago Bay 5ώPearl Culture

7῍9cm Pearl oysters are used for pearl Foot Fishermen move the pearl oysters to areas which are culture. They grow abtbout 3-5cm suitable for each season. long for the first year, and 7-9cm Pearl after 3 years. That’s when they indicates the number of pearl oysters Mantle are used to make pearls. Gills Adductor muscle In spring , fishermen move the In summer , fishermen move the oysters ẔProduction Process of Pearl Cultureẕ oysters from a southern, warm bay to to the center of the bay or other bays to Ago Bay to insert the cores. avoid high water temperatures. Jan. Feb. Mar. Apr. May Jun Jul. Aug. Sep. Oct. Nov. Dec. ίApr. ῍ Jun.ᾉ 80 ῍100 millionὸ ίJul.῍Sep.ᾉ 80 ῍90 millionὸ Seed production New seeds are Spring Apr. Summer Aug. artificially produced Cultivation ί ὸ ί ὸ First year Cleaning Winter Pearl oysters are Newborn pearl oyster Pearl fishermen moved to a warm bay, Outer Ago Bay Outer Ago Bay clean oysters by because they are Gokasyo bay Gokasyyyo bay machine. susceptibletocold. Matoya bay Matoya bay Toba bay Toba bay Nanto Nanto other Second other year Cultivation In autumn,,y the oysters stay where In winter, fishermen collect mature Fishermen Fishermen control the conditions they are for treatment. insert a pearls and move the 2-year-old pearl of oysters before inserting the core Throughout core and a oysters to a southern, warm bay. the winter piece of mantle ίOct. ῍ Nov.ᾉ 65 ῍80 millionὸ ίDec.ᾉ 36 million, Jan.῍Mayᾉ6 millionὸ tissue into Control oysters conditions the oysters. Operation the core Autumn ίOct.ὸ Winter ίJan.- May.ὸ Cultivation Harvest Outer Ago Bay Third Pearl oysters Outer Ago Bay year are raised very Gokasyo bay Gokasyo bay carefully under Matoya bay Matoya bay a raft until Toba bay Toba bay cultivation. Nanto Nanto other other

ͤNumber of oysters in 2003. Collect the pearls from the oysters. ()indicates number of oysters in Ago Bay. 5ώPearl Culture 5ώPearl Culture Changes in Pearl Production in Ago Bay Pearl Culture and Ago Bay

Land The pearl culture is the main industry in Shima city . Good Collec- tion

㻢㻜 ί1965-ὸ Decline of pearl culture due to low quality & overproduction 䠄㼠䠅

on (t) 㻡㻜 㔞㔞 ii Cleaning 㻠㻜 ί 1992ὸ Mass mortality of pearl Filtering oysters due to red tides of 㻟㻜 (Heterocapsa circularisquama) oysters Feces in Mie ί1996ὸ Widespread Good and 㻞㻜 disease. ┴䛾┿⌔⏕⏘ of pearl product of pearl Bad remains

㔜㔜 Bad 㻝㻜 Continuation Sea bottom ୕ of infectious Oxygen deficient water almost every year disease Amount 㻜 㻝㻥㻞㻡 㻝㻥㻟㻡 㻝㻥㻠㻡 㻝㻥㻡㻡 㻝㻥㻢㻡 㻝㻥㻣㻡 㻝㻥㻤㻡 㻝㻥㻥㻡 㻞㻜㻜㻡 The pearl culture has both good and bad points for the environment. Changes in pearl production in Mie prefecture ẔGood pointsẕ After WWϩ, pearl production increased sharply because of Pearl oysters eat phytoplankton by filtering seawater, thereby exports to America. However, the environment of Ago Bay cleaning the seawater in Ago Bay. Not only pearls but the oyster meat can be collected, too. deteriorated because of overcultivation. In the inner bay, many pearl oysters died due to an outbreak of hydrogen sulfide. ẔBad pointsẕ After filtering the oyster’s feces are dropped to the sea bottom. From 1975῍1985, the pearl production increased because of If fishermen cultivate many oysters, large amounts of feces higggh economic growth and increasing demand from foreig n accumulate. countries. But after the bubble economy collapsed (1994), the It is necessary to remove the attached organism when producing demand for pearls stagnated, and pearls suffered mass death from pearls. If fishermen throw these attached organisms and oyster meat into Ago Bay, the sea bottom becomes dirty. Also when harmful red tides (Heterocapsa circularisquama) and infectious oysters die, their remains accumulate on the bottom. disease.

Pearl production is still in a slump, due to the deterioration of Fishermen should pick up the waste from cleaning, use oyster meat and prevent oysters from dying. the environment and the diversified tastes of customers. 6ώSediment and Water 6ώSediment and Water Sediment and Water Quality in Ago Bay The sediment is getting more eutrophic every year due to accumulating organisms. However, the seawater has not changed.

ͤCOD indicates the amount of organisms. Dirty 㻢㻜 Sediment quality y Ἶ㻕 rr d 㻠㻜 㻛㼓஝ 㻞

㻞㻜 㻰䠄㼙㼓㻻 㻻㻻 㻯 Clean 㻜 Distribution of sediment in Ago Bay 㻝㻥㻣㻡 㻝㻥㻤㻜 㻝㻥㻤㻡 㻝㻥㻥㻜 㻝㻥㻥㻡 㻞㻜㻜㻜 㻞㻜㻜㻡ᖺ NlNormal EtEutrop hic HthiHypertrophic Dirty 㻝㻜 Water quality Although Ago Bay looks fine environmentally, large amounts of 㻤

eutrophic sediment have accumulated on the sea bottom. The sediments 㻛㼘㻕 㻞

㻻 㻢

can be classified in 3 types (normal , eutrop hic , h ypertro phic ). Most 㼓㼓 sediments belong to “eutrophic” and “hypertrophic”, with “normal” in 㻠 the bay mouth only. The sediment at the bay mouth is brown sand. The 㻯㻻㻰㻔㼙 sediment at the inner part of the bay is black mud. 㻞 Clean 㻜 㻝㻥㻣㻡 㻝㻥㻤㻜 㻝㻥㻤㻡 㻝㻥㻥㻜 㻝㻥㻥㻡 㻞㻜㻜㻜 㻞㻜㻜㻡ᖺ More than 50 years ago, Ago Bay was not eutrophic. Why did Ago Bay become eutrop hic ? How Ago Bay become clean? Many researchers are trying to restore the environment

Sediment at bay mouth Sediment at inner part of bay in Ago Bay. 7ώAutomatic Environmental Monitoring System 7ώAutomatic Environmental Monitoring System Ago Bay Automatic Environmental Monitoring System ẔPCẕ 5 monitoring results Time series behavior Distribution of monitoring buoys in Ago Bay SHIMA Branch(Server)

SHINMEI Mie Fisheries Research Institute

Inner part of bay Bay Contour mouth Center The results of monitoring can be HUNAKOSHI of bay seen on the following URL by PC. ίhttp://www.agobay.jp/agoweb /index.jspὸ

Buoy in bay mouth ẔCell phoneẕ

Buoy inner part of bay It is necessary to know the present status of Ago Bay for environmental restoration. Therefore, the Ago Bay automatic environmental monitoring system was adopted. This system monitors the water quality automatically every hour. The 5 monitoring buoys can monitor water temperature, salinity, dissolved oxygen, chlorophyll-aanda, and turbidity. This monitoring system is used not only by researchers but also by pearl fishermen.

The resul ts o fmon itor ing can be seen on t he Sensor following URL by cell phone. The results of monitoring can be seen ίhttp://www.agobay.jp/agoweb_i/index.jspὸ on a PC or cell phone anytime and anywhere. 2-dimensional barcode 8ώWater Quality 8ώWater quality

Understanding Water Quality in Ago Bay ẔSalinityẕ We can see the effects of rain in Ago Bay. Generally, the salinity of the bay is 33-35. After heavy rains salinity We can see the ppqyygresent status of water quality by using the drops below 30 . Although pearl oysters don’t die due to low salinity, it monitoring system. is necessary to monitor it, because low salinity (below 25) has a damaging effect on the quality of pearls. ẔWater Temperatureẕ We can monitor the water temperature. 26 29 32 35 Bay mouth For example , the best temperature for pearl oysters is 13 ῍27Υ. 0 If the water temperature is too high (above 27Υ) or too low (below 13Υ), 5 Salinity of bay mouth is stable the pearl oysters are apt to die. 10

ὸ 15

m 20 ί ὸ

6 11 16 21 26 31Υ th Low salinity from rain pp

25 mm Bay mouth ขข ί De 0 ൦ 0 Inner part of bay 5 5 Salinity of inner part of bay 10 is influenced by rain

ὸ 10

m 15 ί Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 20 hh 25 ẔDissolved Oxygenẕ We can monitor the amount of oxygen.

Dept Inner part of bay 0 Living things cannot survive below 3mg/L of DO. If phytoplankton 5 10 increase excessively, the DO rate becomes too high at this depth. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 2 4 6 8 10mg/l Bay mouth 0 The water temperature in the bay mouth is relatively stable 5 DO of bay mouth because of the influence of the outer sea. However, water 10 is stable ὸ

ὸ 15

temperature in the inner part of the bay changes significantly mm m ί 20 because of the influence of air temperature. 25 Inner part of bay

൦ขί 0 Depth Chlorophyll-a We can see the amount of phytoplankton, bait, and 5 DO of inner part of bay Ẕ ẕ can drop easily observe the occurrence of red tides. 10 ṺHigh Chlorophyll-a Ѝ large amount of phytoplankton Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec ṺLow Chlorophyll-a Ѝ small amount of phytoplankton Phytoplankton increase at Low DO around sea this depth bottom ίbelow 3mg/lὸ 8ώWater Quality 8ώWater quality Phytoplankton in Ago Bay Diatom

The amount of ppyhyto plankton is small from winter to s prin g. In Ma y,

they begin to increase, and the numbers go up and down depending on 50ᾼ 50ᾼ 50ᾼ climate and nutrients. Generally, phytoplankton increase in spring and autumn, but in Ago Bay they increase in autumn only. Chaetoceros sp. Skeletonema cestatum The amount of phytoplankton is checked by using a microscope or analyzing the chlorophyll-a.

0 4 8 12 16 20g/l 50ᾼ 20ᾼ 20ᾼ ẔChlorophyll-aẕ Eucampia zodiacus Nitzschia sp. Asterionella graciallis 0 Bay mouth 5 Dinophyta 10

ὸ 15 mm

ί 20 25 10ᾼ 30ᾼ 100ᾼ

Depth Inner part of bay 0 Prorocentrum dentatum Ceratium furca Noctiluca scintillans 5 (illuminated at night) 10 Harmful and toxic kinds Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Phytoplankton increase ίFrom Ago Bay monitoring system ὸ

10ᾼ 10ᾼ 20ᾼ Generally, diatom and dinophyta are on the increase. Diatom are ingested by bivalves such as pearl oysters. There are harmful and Heterocapsa Karenia mikimotoi Alexandrium catenella toxic plankton in the dinophyta family. Therefore, it is necessary to Circularisquama (Highly toxic for react quickly to outbreaks of dinophyta. (Cause of shellfish (Highly toxic for bivalves) bivalves and fish) poisoning) 8ώWater Quality 8ώWater quality Water quality in the inner part of the bay changes seasonally Seasonal Changes in Water Quality because of the strong effect of climate. In the following charts, red indicates a high value, blue indicates a low value. In winter water temppperature is the same at all depths. In summer surface temperature is high , Water while bottom temperature is relatively low. 䠅 temp ίΥὸ m 䠄

High temperatures from

Depth surface to sea bottom because of hot summer.

In the rainy season, surface salinity is especially low. Salinity 䠅 m 䠄 Depth

DO at sea bottom is low from summer to autumn. In winter DO at sea bottom is high. DO ίmg/lὸ 䠅 m 䠄 Depth

Phy top lan kton increase from summer toau tumn. Chlorophyll-a

ίug/lὸ 䠅 m 䠄 pth ee D

2003 2004 2005 2006 9ώSeawater Flow and Seawater Exchange 9ώSeawater Flow and Seawater Exchange Causes of Seawater Currents Tidal Currents and Residual Currents Eastward Current Velocity (cm/sec)

Position of the Moon and the Sun Position of the Moon and the Sun Neap Tide Spring Tide Neap Tide a floor (m) during Spring Tide during Neap Tide ee Increscent Moon

Seawater

Full S above Elevation Eastward Residual Current Velocity (25 hours mean) (cm/sec) New Moon (m) Moon Revolution Revolution oro Sun Sun Earth Earth Seawater

Decrescent Moon flo Sea above levation EE ᵏᵎᵍᵏᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵔ ᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵏᵏ ᴾᴾ ᵏᵎᵍᵏᵔᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵐᵏ Water Mass Tidal ElevationWater Depth (October at Wanko-ADCP 1 03– Oct 20, 2003) 2003 26 ᵏ Acoustic Wave

25ᵎ Takonobori ᵣᶊᶃᶔᵿᶒᶇᶍᶌᴾᵆᶋᵇ ter Depth(m) ter ADCP aa

ᵋᵏW 24 Neap TideSpring Tide Neap Tide (Acoustic Doppler

ᵲᶇᶂᵿᶊᴾ Current Profiler) ᵏᵎᵍᵏᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵔᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵏᵏᴾ31 32 33 34 35 36 37 38 39 40 41ᴾ 42 43 44 45 ᵏᵎᵍᵏᵔᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᴾᵏᵎᵍᵐᵏ 46 47 48 49 50 51 Sea Floor Day s

Flows or currents of water in the coastal sea are generated by various Seawater drawn into the bay during high tide returns to the outer sea. This sources of energy like tides, wind, solar radiation, rain precipitation and period of time when the outward current velocity is maximized is called an changes in water density in the outer sea. Tides create a difference of ebb tide. Conversely, the period of time when the seawater flows into the bay thickness in seawater on the earth’s surface as shown in the above figures. is called a flood tide. The flow caused during the flood and ebb tides is known The gravitational forces of the sun and the moon make the seawater thickness as a tidal current. uneven. High and low tide take place on the thick and thin areas, respectively. The top figure shows the velocity data of the eastward tidal current When the moon is in line with the sun (upper left figure), the gravitational measured by the ADCP on the sea floor at ‘Takonobori’ during October 2003. force acting on seawater is intensified and the difference of water surface The site location is indicated on the map . The vertical axis of the figure shows elevation between high and low tide is maximized. This corresponds to spring the elevation above the sea floor. The colors represent intensity and direction tide. When the moon stands perpendicular to the sun (upper right figure), the of currents. The red and blue colors correspond to the east and westward gravitational force is weakened and the difference of water surface elevation currents, respectively. Strong currents were recorded during spring tide, while between high and low tide is minimized. This corresponds to neap tide. relatively weaker currents occurred during neap tide. This can be seen in the observation data of sea surface levels recorded at The middle figure shows the data obtained by a time-average of 25 hours on Ago Bay during October 2003, where the spring and neap tide occur the same data shown in the top figure. The current determined by this periodically almost every 15 days. This period corresponds to the moon’s mathematical operation is called a tidal residual current, or simply, residual revolution around the earth. The half-diurnal change of sea level is due to the current. It is the residual current that mainly affects the movement of revolution of the earth. substances in the ocean. Thus, the residual current strongly affects water quality of the bay. 9ώSeawater Flow and Seawater Exchange 9ώSeawater Flow and Seawater Exchange The Complex Flow near Kashiko Island The Tidal Currents in Tategami and Funakoshi Inlets

Data Recorded at 4pm August 4, 2005 Data Recorded at 8am June 20, 2005 ᵲᵿᶒᶃᶇᶑᶆᶇ ᵧᶌᶊᶃᶒ 㻭 㻣㻢

㻠㻜 㻮 㻞㻢 㻝㻣㻡 ᵲᵿᶒᶃᶅᵿᶋᶇ 㻡㻢 㻞㻢 ᵧᶌᶊᶃᶒ ᵩᵿᶑᶆᶇᶉᶍ ᵧᶑᶊᵿᶌᶂ 㻝㻝㻞

ᵳᶅᵿᶒᵿ ᵧᶌᶊᶃᶒ 㻯 㻝㻜㻣 㻤㻜 㻤㻜 㻟㻤 ᵲᶍᶋᶍ ᵫᶒᵌ ᵦᶃᵿᶂᴾᶍᶄᴾᵲᵿᶒᶃᶅᵿᶋᶇ ᵧᶌᶊᶃᶒ 㻞㻡㻠 㻠㻞 Eddy 㻝㻤㻞 ᵷᶍᶉᶍᶗᵿᶋᵿᴾᵧᶑᶊᵿᶌᶂ ᵭᶆᶑᵿᶉᶇ ᵲᵿᶒᶍᶉᶓ ᵧᶑᶊᵿᶌᶂ 㻥㻡 ᵢᶍᶇᶅᵿᶆᵿᶐᵿ ᵧᶑᶊᵿᶌᶂ The next picture shows flow patterns in Tategami Inlet during ebb tide. The 㻠㻤㻞 Sattelite most important point is that the discharge takes place simultaneously through th e thr ee ch ann els (A ,B an d C) th at conn ect th ein let to th e outerr egi on . GPS Acoustic Doppler Current Profiler Similar trends were also observed during flood tide. These features are evidence Sea Surface The yellow arrows show the magnitude and that the inlet is positioned at the innermost part of Ago Bay in a hydro-dynamic direction of currents. The numbers show the flow sense. This could explain the lower quality of seawater and sediment in the Acoustic Wave rate (ton/s) through the cross section marked by the white line. Same in the following two pictures. inlet. Sea Floor

This picture shows the complex flow pattern near Kashiko Island during flood The left picture shows the flow tide. The flow from the bay mouth divides into northward and eastward flows at pattern in Funakoshi Inlet during flood the southern edge of Tatoku Island. The northward flow heads for Ugata Inlet, tide. The most instructive point is the while the eastward component goes to the narrower channel between Yokoyama contribution to water exchange by the and Doigahara Islands. A portion of the northward flow turns east at the north- Fukaya canal, which directly connects western area of Tatoku Island and heads for Shinmei Inlet. The eastward flow in the inner part of the inlet to the the southern and northern channels of Tatoku Island joins together at the north- Pacific Ocean. As shown, the flow rate eastern area of Tatoku Island and goes on toward Shinmei and Tategami Inlet. to Katada port from the Funakoshi The reverse (westward) flow along the northern coast of Tatoku Island indicates the occurrence of an eddy and implies the complexity of flow patterns Inlet is more than that from the F u kay a there. The data shown herein including those on the following page were canal. This shows the canal’s measured by an ADCP attached to a small vessel. limitations concerning water quality Data Recorded at 2pm September, 2005 enhancement to Fukaya Inlet. 9ώSeawater Flow and Seawater Exchange 9ώSeawater Flow and Seawater Exchange The Residual Flow of Ago Bay in Summer The Residual Flow of Ago Bay in Winter

ᵟᶔᶃᶐᵿᶅᶃᴾᶄᶐᶍᶋᴾᵨᶓᶊᶗᴾᶒᶍᴾᵱᶃᶎᶒᶃᶋᶀᶃᶐᴾᵐᵎᵎᵑ ᵟᶔᶃᶐᵿᶅᶃᴾᶄᶐᶍᶋᴾᵨᵿᶌᶓᵿᶐᶗᴾᶒᶍᴾᵫᵿᶐᶁᶆᴾᵐᵎᵎᵒ

Numerics : Flow Rate(ton/sec) Numerics : Flow Rate(ton/sec) 㻞㻚㻝 㻝㻚㻝 㻞㻚㻝 㻝㻚㻝 㻝㻞 㻞㻚㻣 㻞㻚㻥 㻟㻚㻤 㻝㻞 㻝㻚㻜 㻞㻚㻥 㻠㻚 㻟㻚㻥 㻡㻚㻝 㻥

㻝㻟 㻝㻞 㻡㻚㻜 㻢㻚㻞㻣㻚㻣 㻝㻞 㻝㻞 㻟㻢 㻞㻚㻟㻝㻜 㻝㻞 㻝㻚㻜 㻟㻞 㻝㻝 㻢㻚㻢 㻝㻚㻢 㻠㻜 㻜㻚㻡 㻢㻚㻠 㻞㻚㻡 㻝㻚㻝 㻞㻚㻣 㻟㻢 㻣㻝 㻠㻣 㻝㻚㻝 㻝 㻝㻢㻣 㻞㻣 㻞㻚㻡 㻝㻞㻝 㻝㻣㻥 㻢㻣 㻢㻚㻢 㻝㻢㻤 㻤㻝 㻝㻝㻡 㻝㻞 㻞㻚㻟 㻜 㻝㻣㻥 㻝㻜㻥 㻞㻚㻠 㻜㻚㻥 㻥㻚㻟 㻟㻚㻞 㻝㻜㻝 㻞㻝 㻞㻚㻣 㻞㻝 Flow Direction 㻞㻚㻣 Flow Direction 㻞㻝 ᵳᶎᶎᶃᶐᴾᵪᵿᶗᶃᶐᴾᵆᶆᶍᶐᶇᶘᶍᶌᶒᵿᶊᵇ ᵳᶎᶎᶃᶐᴾᵪᵿᶗᶃᶐᴾᵆᶆᶍᶐᶇᶘᶍᶌᶒᵿᶊᵇ ᵪᶍᶕᶃᶐᴾᵪᵿᶗᶃᶐᴾᵆᶆᶍᶐᶇᶘᶍᶌᶒᵿᶊᵇ ᵪᶍᶕᶃᶐᴾᵪᵿᶗᶃᶐᴾᵆᶆᶍᶐᶇᶘᶍᶌᶒᵿᶊᵇ ᵳᶎᶕᶃᶊᶊᶇᶌᶅ ᵳᶎᶎᶃᶐᴾᵪᵿᶗᶃᶐᴾᵘᴾᶑᶃᵿᴾᶑᶓᶐᶄᵿᶁᶃᴾᶒᶍᴾᵒᴾᶋᴾᶕᵿᶒᶃᶐᴾᶂᶃᶎᶒᶆ ᵳᶎᶕᶃᶊᶊᶇᶌᶅ ᵳᶎᶎᶃᶐᴾᵪᵿᶗᶃᶐᴾᵘᴾᶑᶃᵿᴾᶑᶓᶐᶄᵿᶁᶃᴾᶒᶍᴾᵒᴾᶋᴾᶕᵿᶒᶃᶐᴾᶂᶃᶎᶒᶆ ᵢᶍᶕᶌᶕᶃᶊᶊᶇᶌᶅ ᵪᶍᶕᶃᶐᴾᵪᵿᶗᶃᶐᴾᵘᴾᶀᶃᶊᶍᶕᴾᵒᴾᶋᴾᶕᵿᶒᶃᶐᴾᶂᶃᶎᶒᶆ ᵢᶍᶕᶌᶕᶃᶊᶊᶇᶌᶅ ᵪᶍᶕᶃᶐᴾᵪᵿᶗᶃᶐᴾᵘᴾᶀᶃᶊᶍᶕᴾᵒᴾᶋᴾᶕᵿᶒᶃᶐᴾᶂᶃᶎᶒᶆ

It is essential to investigate the path of the flow around Ago Bay as well as The flow direction in winter is almost opposite to that in summer. Thus, the the flow rate, when talking about water quality. The data depicted above flow in the upper and the lower layer head for the bay head and the bay was obtained by a three-dimensional hydrodynamic computer simulation. It mouth, respectively. The north-west wind (monsoon) which dominates in shows the directions and the flow rates of the residual current in the upper winter is the cause of this flow pattern . The density stratification diminishes and lower layers at the transverse sections placed in the channels of the bay. and the density difference between the bay and the outer sea also weakens As described in the previous pages, the residual current plays the primary role as winter progresses, and the influence of wind becomes significant. of substance (e.g., oxygen) transportation and has a strong connection to As seen in the data of residual flow in summer, there also exists a big water quality. All flow directions in the upper layer go to the bay mouth, difference in the flow rate between the bay mouth and the bay head area in while those in the lower layer go to the bay head. This type of flow pattern, winter. The magnitude of residual flow velocities in the upper layer are about called an estuarine circulation, is caused by the water density difference 2cm/s (summer) and 3cm/s (winter) in the bay mouth area, while those in between the bay and the outer sea. The high water temperature from solar Tategami Inlet are about 0.8mm/s (summer) and 1.3mm/s (winter). The heating and the salinity decline from river discharge promote a decrease in difference is more than 1/20. The stagnation period of substances calculated water density in the bay . The flow pattern shown above occurs because the from the flow rate is a few days in the bay mouth area and a few dozen days gravitational force acts to push lighter water toward the outer sea where the in Tategami Inlet. These physical aspects are the fundamental cause of the water density is relatively high. big difference in the quality of seawater and sediment between the bay mouth and the bay head area. 9ώSeawater Flow and Seawater Exchange 9ώSeawater Flow and Seawater Exchange Intrusion of Oceanic Seawater, Triggered by North- Seawater Exchange in Winter by Monsoon Western Wind (Spring, Summer, Autumn) North-Western Wind Wind Driven Current Bay Head Southward Movement Bay Head

Intrusion of High Relatively High Salinity Water Temperature and Bay Mouth Salinity Bay Mouth

Bay Mouth Takonobori Relatively Low Temperature NW Maxima of w Upwelling i and Salinity nd Seawater Vertical Cross Section of Ago Bay Density Upwelling of N High Salinity W NW (Schematic) w N w in W i WtWater d w nd Vertical Cross Section of Ago Bay in ᇌᅕޅ d (Schematic) High Salinity Water Observation Data in 2003 Movement of Surface Water Period of NW Wind Blowing Outer Sea Wind Velocity and Direction

Wind Velocity and Direction

Salinity outside of Bay Mouth

Eastward Residual Current Velocity at Takonobori (cm/s) ter Depth (m) aa ee W Eastward Residual Current Velocity at Takonobori (cm/s) Sea Floor (m) Floor Sea Elevation abov Elevation 1/2 8 14 20 26 2/1 7 13 19 25 3/2 8 14 20 26 30 Sea Floor Sea Floor (m)

Elevation above above Elevation 9/22 26 10/2 8 14 20 26 11/1 7 13 19 25 12/1 The seawater exchange between the bay and the outer sea has a strong As described earlier, the wind-driven current caused by the monsoon effect on the water quality of the bay. In Ago Bay, during Spring to Autumn, strengthens from January to March, and this causes another type of seawater the high salinity water of the outer sea intermittently intrudes into the lower exchange. The observation data above shows that the eastward residual layer of the bay, which triggers seawater exchange. It is known that this current velocity near the sea surface is strengthened when the monsoon wind intrusion is connected to the occurrence of the north-western wind. When the (north-western wind) blows hard and continuously. The current strength is NW wind blows, the wind force conveys water near the sea surface to the intense within the thin layer just below the sea surface. The reverse flow south. Concurrently, the more saline water in the deeper sea moves toward toward the bay mouth (westward) in the middle and lower layers the shallower sea. This phenomenon is called upwelling. If the high salinity complements the wind-driven current. water rises beyond the sea floor height of the bay mouth, the water rushes The strength of seawater exchange is expressed by the number of days in into the lower layer of the bay. The observation data shown above depicts which the entire water in the bay is exchanged with the outer sea. The the relation between the wind, the salinity outside of the bay and the number of days of seawater exchange for Ago Bay is calculated in our eastward residual current velocity at Takonobori. Upwelling of seawater is research at about 24 days in summer and 16 days in winter. caused by the rise in salinity. 10ώPresent Status of Ago Bay 10ώPresent Status of Ago Bay Environmental Problems in Ago Bay Ṻ Causes of sediment eutrophication

In Ago Bay, large amounts of eutrophic sediment have ẔṞ NiNutrient Loadfd from Landẕ accumulated on the sea bottom. As a result, red tides Because forests exist very close to the sea, nutrient loads flow and hypoxia occur frequently. swiftly into Ago Bay. As a result, phytoplankton increase and it’s This is a big environmental problem for Ago Bay! easy for red tides to occur. Ẕṟ Decrease in Catchesẕ Until 1960, more than 600t of fish were caught in Ago Bay.

Ṟ Nutrient load from land ṟ Decrease in catches However since 1965, little has been collected except for pearls and laver. Therefore picking up nutrients from Ago Bay has RED TIDE dddecreased. Absorb Poor water exchange ẔṠ Decrease in Tidal Flats and Sea Grass Bedsẕ Tidal flats and seagrass beds have the function of preventing Decompose ṡ Nutrient load sediment eutrophication. In Ago Bay, more than 70% of tidal flats from pearl oysters deteriorated due ro land reclamation. As a result, the natural Ṡ Decrease in tidal flats and sea grass beds purification capacity has become very small. Hypoxia ᶣ

Accumulation of Ẕṡ Nutrient Load from Pearl Oysters ẕ eutrophicἪἛἿỉؚᆢ sediment Pearl culture is the basic industry of Ago Bay. However, if fishermen don’t pick up the waste from cleaning and pearl oyster meat, sediment eutrophication will increase. 11ώRed Tides 11ώRed tides Red Tides Checking for Red Tides

Red tide is a common name for a phenomenon where By using the Ago Bay monitoring system, we can see the phytoplankton increase explosively in seawater. As a result, present status of red tides and hypoxia on a PC or cell seawater becomes discolored (red, green or brown). phone anytime and anywhere.

ẔRed Tide Kills Bivalvesẕ ẔCCgCpyhecking for Chlorophyll-a byyC PCẕ In 1992, a red tide formed by new phytoplankton (Heterocapsa 2004 Inner part of bay ίTATEGAMIὸ high Circularisquama) occurred in Ago Bay. After 1992 this red tide Diatom has often occurred and damaged pearl culture.

low 9/1 3 5 7 Diatom gradually sink to the sea bottom. Diatom are good food for pearl oysters.

2004 Inner part of bay ίTATEGAMIὸ ͤthese dinophyta are Heterocapsa circularisquama A red tide of Heterocapsa Circularisquama Pearl oysters killed by high ίAt TATOKU i sl and , 13 A ug ., 2004 ὸ Heterocapsa Circularisquama Dinophyta ẔLarge Amounts of Phytoplankton are Bad for the Environmentẕ Large amounts of diatom, which is food for pearl oysters, is not good for the environment , because these diatoms will die and accumulate on the sea bottom. As a result, oxygen deficient low water occurs. 8/89 10111213141516 Phytoplankton need nutrients. If large amounts of nutrients Dinophyta move up and down because they can swim. During flow into Ago Bay, a red tide will occur. Our lifestyles are the daytime dinophyta move to the surface , while at night they move to the bottom. related to red tides, because large amounts of nutrients are ͤWhen a high chlorophyll-a pattern moves up and down on discharged by our way of living. the monitoring system, this indicates a red tide of dinophyta. 12ώHypoxia in Ago Bay 12ώHypoxia in Ago Bay Hypoxia in Ago Bay Checking for Hypoxia ẔChecking the DO on a PCẕ Hypoxia is a phenomenon that occurs as dissolved oxygen 2004 Inner part of bay ίTATEGAMIὸ becomes reduced in concentration (below 3mg/l) to a point high detrimental to aquatic organisms living in the system. In Ago Bay hypoxia occurs every summer. DO HiHypoxia ẔThe Menace of Hypoxiaẕ In Ago Bay, hypoxia occurs every year. Especially from Jun. to low Oct. dissolved oxygen from the center to the inner part of the 8/1 8/15 8/31 bay decreases. Fish can escape hypoxia, but aquatic organisms ẔChecking the DO on a Cell Phoneẕ living on the sea bottom such as shellfish and polycaeta die. In This figure indicates that the DO on the sea ᒍᖐฺ࿢ؾ 2002, large scale hypoxia occurred in Ago Bay, and pearl culture ⋔⋇⋁⋙⋞⊹⋟⊽⊾⋄⋒ bottom is greatly decreased by hypoxia. andflddd aquatic organisms were significantly damaged. Ⅸ ᒍ ᖐ ฺ Ⅹ We can see the monitoring data on a PC or ښ ⅌ฺ cell phone. Let’s check the changes in water ẔHypoxia is Not Good for the Environmentẕ 2004࠰08உ15ଐ 14:00 In summer, aquatic organisms disappear in the inner part of the quality in Ago Bay. ෙ᩿ɦ≔⊐ bay because of hypoxia. Hypoxia damages not only fisheries but ⅌൦ ภ 30.0 Υ PC ᾉ http://www.agobay.jp/agoweb/index.jsp Ў 28.4 psu ط⅌ also natural purification capacity. ⅌ ๋܍ᣠእ Cell phoneᾉ 10.4 mg/l http://www.agobay.jp/agoweb_i/index.jsp Bay mouth ෙࡁɥ≔⊐ ⅌൦ ภ 25.4 Υ Ў 33.3 psu ط⅌ ⅌ ๋܍ᣠእ 0.1 mg/l Hypoxia

Inner part of bay Mie Fisheries Research Institute gives information on phytoplankton every week. We can see the water quality in Ago BAY at the following URL. Mass mortality of bivalves by hypoxia Hypoxia areas in Ago Bay ίhttp://www.mpstpc.pref.mie.jp/SUI/kankyo/ὸ ίat UGATAHAMA Oct., 2002ὸ 12ώHypoxia in Ago Bay 12ώHypoxia in Ago Bay The Causes of Hypoxia ṟ Accumulation of organic materials The causes of hypoxia are Ṟ deterioration of the Hypoxia may also occur when the wastes from pearl culture and oxygen supply to the sea bottom and ṟ accumulation dead phytoplankton accumulate on the sea bottom. of organic materials on the sea bottom. Phytoplankton increase due to nutrient Nutrient load Ṟ Deterioration of the oxygen supply supply from the land. Organic materials In Ago Bay, the mixing processes of seawater are different Phytoplankton accumulate on the sea bottom because every season. dead phytoplankton and the wastes

儈充兠儜僸⾲♧働傳僤僁價傏充兆兎୙㊊僔僅僧僑儈充兠儜僸㛤債傹僎傲働傳僐傪傱傎儈充兠儜傲◚ᦆ傽僌傪僱ྍ⬟ᛶ傲储僰僤傿傏儗兗儸光兠儣 僸෌㉳ື傽僌෌ᗘ儹儅儈兏僸㛤傪僌債僆傻傪傏僃僲働僨㉥傪 x 傲⾲♧傻僲僱ሙྜ僕傎儈充兠儜僸๐㝖傽僌ᤄධ傽僌債僆傻傪傏 Dead phytoplankton from pearl culture sink. To decompose In summer, the weight of surface Wastes from pearl culture these organic materials, bacteria use water becomes light because of O 2 larggyge amounts of oxygen in the seawater. O2 O2 O O2 warming and low salinity due to rain. 2 As a result, oxygen at the sea bottom On the sea bottom, there is high Organic materials Oxygen decreases at the sea bottom≆ decreases immensely. salinity and relatively cold, heavy water. That’s why in summer seawater ẔSummerẕ doesn’ t circulate well and oxygen Ṟὺṟ ᾉ Hypoxia occurs in summer in A go Ba y

cannot be supplied to the sea bottom. 儈充兠儜僸⾲♧働傳僤僁價傏充兆兎୙㊊僔僅僧僑儈充兠儜僸㛤債傹僎傲働傳僐傪傱傎儈充兠儜傲◚ᦆ傽僌傪僱ྍ⬟ᛶ傲储僰僤傿傏儗兗儸光兠儣僸෌㉳ື傽僌෌ᗘ儹儅儈兏僸㛤傪僌債僆傻傪傏僃僲働僨㉥傪 x 傲⾲♧傻僲僱ሙྜ僕傎儈充兠儜僸๐㝖傽僌ᤄධ傽僌債僆傻傪傏 As mentioned, hypoxia occurs in summer because seawater cannot

Little rain In winter, the weight of surface circulate and the decomposition of water bhbfbecomes heavy because of orgiganicma tiliterials increases. As a resu lt, O2 Weak sunshine O2 cooling and little rain. The heavy oxygen is depleted on the sea bottom The surface water is cools and sinks surface water sinks to the bottom. and aquatic organisms die. Therefore, in winter, seawater is naturallyyyg mixed and oxygen can be Seawater circulates! ≋Oxygen supply is refreshed≆≌ ẔWinterẕ supplied to the sea bottom.

When the organic materials on the sea bottom decompose, oxygen is consumed. Hypoxia occurs when the amount of In summer, because seawater cannot circulate and sufficient oxygen consumption becomes larger than the oxygen supply. To quantities of oxygen cannot reach the sea bottom, hypoxia is prevent hypoxia, it is necessary to reduce the accumulation of apt to occur. organic materials. 13ώAccumulation of Organic Materials and Purification Capacity Historical changes in Natural Purification Capacity and Accumulation of Organic Materials in Ago Bay Ϩ Before Meiji era (⊡1868)≝Natural purification capacity ӑ Accumulation of organic materials In Ago Bay , hypoxia is a very serious problem . Nutrient load (small) Fisheries uptake ⅨNatural Purification CapacityⅩ (large) Many tidal flats and seagrass To remove hypoxia, it is important to keep the balance between natural purification and the accumulation of organic materials. Before the Meiji era, beds existed and large amounts of Uptaking Phytoplankton natural purification capacity was higher. However, it decreased because more fish were gathered by fisheries. (POM) than 70% of tidal flats were reclaimed, and organic materials increased due to population growth and pearl culture. Unfortunately, the accumulation of ⅨAccumulation of Organic organic materials is higher now than the natural purification capacity of Ago Bay. Decomposing Sedimentation MaterialsⅩ (small) ℴ Tidal flats and Nutrient loads were small and

ℵ Ac ίImageὸ Accumulation of

c organic materials hardly High organic materialsmaterials High seagrass beds Ⅎ or umulation of ℳ Natural purification accumulated. capacity ℴ ℳ

Organic materials didn’t accumulate in tidal flats and seagrass beds. Aquatic ℵ ℶ organisms could live throughout the year. Red tides and hypoxia didn’t occur. cation capacity g ii Ⅎ anic materials

Low Low ϩ The early Showa era (1926⊡50s)≝Ў Natural purification 17001800 1900 1950 1980 2000 A.D. capacity ӌ Accumulation of organic materialsЌ Natural purif

⃽: Before MEIJIMEIJI ⃾: Early SHOWASHOWA ⃿ :Mid: Mid SHOWA ℀ :Now: Now ℁ : Future Nutrient load (large) Fisheries uptake ⅨNatural Purification CapacityⅩ (large) Tidal flats and seagrass beds Ⅎ 1668 ⊡ : Beginning of reclamation. were reclaimed. Natural ℳ ⊡ 1945 : Large amounts of fish were caught. Redౡཋ tide Uptaking ⇽∏∙⇕⇮∙ purification capacity decreased. ℴ 1892 : Large scale red tide occurred. ⅨAccumulation of Organic ℵ 1950s : Decrease in aquatic organisms due to hypoxia. Decomposing MaterialsⅩ ℶ 1960⊡ : Decrease in fish gathering. Sedimentation (large) Nutrient loads increased and organic materials were apt to Ⅎ 1868⊡1945 : Increase of nutrient load due to population growth. Decrease in tidal flats and seagrass beds due to land accumulate. ℳ 1956 : Large scale hypoxia occurred. reclamation Accumulation of ℴ 1950s : Increase in the accumulation of organic materials by eutrophic sediment rapid growth of pearl culture. ℵ 1960s : Decrease in the accumulation of organic materials by Red tides occurred due to land reclamation. The accumulation of organic depression of pearl culture. materials increased because of sedimentation of phytoplankton. 13ώAccumulation of Organic Materials and Purification Capacity 13ώAccumulation of Organic Materials and Purification Capacity Future Natural purification capacity Ϫ The Showa 30s (1950s῍60s)ᾉNatural purification capacity Ӑ Ϭ ᾉ ᾍ Accumulation of organic materials Accumulation of organic materials ⅨNatural Purification Capacity Ⅹ ṻ It is necessary to enhance natural purification capacity by decreasing IigtitldIncreasing nutrient loads nutrient loads from the land and pearl culture. from land Aquatic organisms died from a Pearl culture decrease in fisheries uptake and Redౡཋ tide Ⅎ Decrease nutrient loads Uptaking ⇽∏∙⇕⇮∙ hypoxia. Increase from land fisheries uptake ℳ Environmentally friendly pearl culture Decomposing ⅨAccumulation of Organic Increasing Phytoplankton sedimentationஊೞཋ↝ؚᆢ of Uptaking organic materials MaterialsⅩ Hypoxia Organic materials were apt to

⁷ Decrease in tidal flats and seagrass accumulate due to increasing Decomposing beds due to land reclamation AltifAccumulation of nutitrien tlt loa dsan dpear lcu lture. eutrophic sediment Decrease sedimentation of Organic materials were apt to accumulate due to the rapid increase of pearl ℴRestoring the tidal flats organic materials culture. Hypoxia and red tides occurred every year. and seagrass beds

Natural purification capacity ≡ ϫ Heisei era ίPresentὸᾉ Natural purification capacity ᾋ Accumulation of organic materials Accumulation of organic materials Ⅎ Decrease nutrient loads from land Increasing nutrient loads ⅨNatural Purification Capacity Ⅹ from land If people try to reduce excess nutrient loads from daily activities, such as Aquatic organisms died from a Pearl culture cooking and washing, sedimentation of organic materials can be decreased. Redౡཋ tide decrease in fisheries uptake and ⇽∏∙⇕⇮∙ Trying environmentally friendly pearl culture Uptaking hypoxia. ṟ Accumulation of Organic If fishermen stop discarding oyster meat and cleaning wastes in an Decomposing Ⅸ Increasing MaterialsⅩ environmentally friendly manner , sedimentation can be decreased. sedimentationஊೞཋ↝ؚᆢ of organic materials In spite of decreasing pearl ℴ Restoring tidal flats and seagrass beds Hypoxia production, organic materials still Decrease in tidal flats and ⁷ If unused reclaimed areas are restored to tidal flats and seagrass beds, the seagrass beds due to land were apt to accumulate due to reclamation Accumulation of biodiversity and natural purification capacity can be enhanced in Ago Bay. eutrophic sediment increasing nutrient loads.

Though the accumulation of organic materials decreased a bit because of the If we try Ṟ, ṟ and Ṡ individually, hypoxia will not disappear. If decline in pearl production, natural purification capacity was still small. As a result, hypoxia and red tides occurred every year. we act on Ṟ, ṟ and Ṡ at the same time, hypoxia may disappear. 14ώTowards Nature Restoration in Ago Bay 14ώTowards Nature Restoration in Ago Bay “What we can all do.” For Nature Restoration in Ago Bay 1ώDecrease the nutrient load from land One of the major nutrient loads from land is household effluents Restoring nature in Ago Bay means that “Ago Bay will become a Sato- from our activities. Livestockအင Umi again with high productivity and biodiversity and pearl culture in Natureᐯ໱ Industry ᵔᵃ harmony with nature.” ငಅ ᵐᵖᵃ ᵑᵎᵃ ḛSurely you don’t think I’m responsible for nature restoration! ” Because we changed the environment of Ago Bay with our human ဃ෇ Household activities, we should restore it. ᵑᵔᵃ For restoration, we propose the following five suggestions. ẔPercentage of nutrients that flow into Ago Bayẕ

People in this region have to be careful 1 Decrease the nutrient load from land ώ to reduce excess nutrients. Be careful not to drain excess nutrient loads We can achieve this by : 2ώDecrease the accumulation of organic materials ὉUsing only necessary amounts of soap and detergent. on the sea bottom. ὉDisposing of cooking oil by absorbing it with paper or cloth. ὉNot allowing garbage to go down the drain. Properly dispose of cleaning wastes and oyster meat etc. 3ώEnhance biodiversityyp and natural purification capacity Septic tanks and sewage systems clean household effluents. The local government promotes the following ways to clean Restore tidal flats and seagrass beds effluents. 4ώTransport organic materials from Ago Bay Ṟ Connecting every home with the sewage system inside the area. Promote fisheries to be able to fish again ṟ Setting up septic tanks in areas outside the sewage system. 5ώTake good care of Ago Bay Not only the people in this region but also visitors to Ago Bay Enjoy a peaceful, ecological life in our Sato -Umi must be careful not to drain excess nutrient loads. If we seriously act upon these five suggestions, a new Sato-Umi will be created. 14ώTowards Nature Restoration in Ago Bay 14ώTowards Nature Restoration in Ago Bay

2ώDecrease the accumulation of organic materials on the sea bottom Ṻ Activities for restoring tidal flats and seagrass beds

It is important to restore continuous natural coastal ecotones (reedsЍtidal Cleaningpearl o ysters is im portant to produce good p earls. However , the flatsЍseagrass beds) where many kinds of aquatic organisms can live . nutrients from these operations cause large problems for Ago Bay. Therefore, it is important to decrease the accumulation of organic materials on the sea bottom by removing the cleaned wastes. And oyster meat is the Ṡ Increasing ṟ Increasing Ṟ Restoring seagrass beds biodiversity in tidal flats tidal flats same. Fisherman should dispose of it properly after taking out the pearl. If all fish ermen dot his, hypox iaw ill disappear. Seagrass beds Tidal flats Reed community Take care not to drain Take care not to drain cleaned wastes oyster meat Ṟ Restoring tidal flats ṟ Increasing biodiversity in tidal flats

After construction The unused areas which were reclaimed more than 50 years ago were Before experimentally changed to tidal flats again. construction Increased Low biodiversity Using a wastewater treatment machine Collecting oyster meat by disposable net biodiversity 3ώEnhance biodiversity and natural purification capacity Many kinds of aquatic organisms Many kinds of aquatic organisms live in tidal flats and seagrass beds. They increased by controlling the Experimental fields in TATEGAMI sediment quality suitable for them. contribute to reducinggg the accumulation of organic materials on the sea bottom. Currently tidal flats and seagrass beds are slowly being restored by Ṡ Increasing seagrass beds local communities. If these restorations continue, biodiversity and natural purification capacity will be enhanced. As a result, red tides and hypoxia Easy methods were developed will disappear from Ago Bay.

A Zostera mat on the sea bottom

After 6 months The Zostera japonica transformed Environmental education Constructing tidal flats Restoring seagrass beds on the sea bottom on tidal flats with fishermen with fishermen 14ώTowards Nature Restoration in Ago Bay 14ώTowards Nature Restoration in Ago Bay 4ώTransport organic materials from Ago Bay The Future of Ago Bay Fisheries have as their function the transport of organic materials Ago Bay will become a New Sato-Umi. from the sea to land areas. However, in Ago Bay there are few fisheries for catching fish and shellfish. Large amounts of organic materials flow into Ago Bay. If there are no fish to catch in Ago Bay, Beautiful rivers all organic materials from the land accumulate on the sea bottom. We shall try to reduce nutrients from the land and catch fish using Many blessings from the bay fisheries at the same time . Let’ s promote locally produced and consumed fish in Ago Bay. ͤ Of course overcatching affects  Fun activities Changes in aquatic products ƦƷ˂Other in Ago Bay ȊȞdzSea cucumber the environment, too.  ǯȫȞǨȓȷǬǶȟPrawn and crab ෙᕹSeaweed ųᲢᳮᲣ  tt ᝝᫏Shellfish ᣽᣽ Pearl culture

๤ྒ  Amoun harmonized with            Large tidal flats the environment Changes of catchment in Ago Bay 5ώTake gggyood care of Ago Bay and seagrass beds

ὉPeople enjoy playing in Ago Bay. ὉPeople take good care of Ago Bay Our love for the bay is vital for its restoration. ḛHave you been to Ago Bay recently? ” Swimming Gathering of clams Pearl culture

Sea kayak Observing Sunset in Ago Bay Eating many fish Being proud of Ago Bay macrobenthos Wonderful sight-seeing

Going fishing Catching fish Bird watching

Sea kayaking Observing macrobenthos in tidal flats If we act on Ṟ, ṟ, Ṡ, ṡ and Ṣ individually, the environment Many visitors Etc. of Ago Bay cannot be restoredIfwed. If we do all these things equally at the same time, then restoration is possible. Let’s build a good partnership with Ago Bay and create First, let’s all do what we can. If everyone tries to do these five things, we can definitely restore Ago Bay. a New Sato-Umi ! 15ώMore Information

For people who want to know more about Ago Bay A Sato-Umi is the coastal area between the actual land and There are many places to learn more about the bay. fisheries with biodiversity and high productivity in terms of Please go there to find out more. human activity . More than 20 years ago, Ago Bay was a Sato-Umi. However, ISE SHIMA National Park SHIMA City Hall social systems drastically changed, and Ago Bay lost it’s identity YOKOYAMA Visitor Center as a Sato-Umi. Ago Library From now on, all the people of this region (inhabitants, visitors Mie Fisheries Research Institute and fishermen) must try not only to restore Ago Bay but also to build a new relationship with the bay, harmonized with present society. In other words, it is important that “everyone in this SHIMA Nature School region has a future vision and acts toward a New Sato-Umi harmonized with the environment in which fishermen continue Society of Wild Animals in SHIMA pearl culture and people enjoy eco -tourism.” SHIMA Library We wrote this booklet because we want you to know about Ago ὉMie Fisheries Research Institute Bay. We will be delighted if this helps you act toward its httpppppjp://www.mpstpc.pref.mie.jp/SUI/index.htm ί ὸ restoration. ὉShima City Hall ίhttp://www.city.shima.mie.jp/ὸ ὉIse Shima National Park Yokoyama Visitor Center ί http://www2.mie-net.ne.jp/iseshima/ὸ The contents of this booklet are a result of the JST-CREATE Program, ὉSociety of Wild Animals in Shima “Project of Environmental Restoration of Enclosed Coastal Seas.” ίhttp://www.e-net.or.jp/user/ikuowaka/ὸ Thanks to this project, a lot was learned about methods to restore Ago Bay. However, we still haven’t learned everything there is to know, and ὉShima Nature School ίhttp://www.shima-sg.com/f_index1.htmlὸ we must keep working to completely restore the environment. ὉAgo Library ὉShima Library ὉMie Prefectural Department of Fisheries ẐMie-no-Umiẑ Apr. 1st, 2011 ίhttp://www.sea.pref.mie.jp/ὸ Editor: Mie Fisheries Research Institute (COE)